This invention relates to an adjustable motorized hospital bed having independently actuable head and foot adjusting mechanisms for elevating and lowering each end of the bed independently of the other end. More particularly, the invention relates to a latching system for maintaining continuous operation of those adjusting mechanisms to lower both ends of the bed to their extreme lower limits, the bed being directly moved to that lowermost level from any tilted or level position.
Adjustable motorized hospital beds are usually vertically movable so that the mattress supporting structure may be established at a selected desired height, within a range of permissible heights, from the floor. To maximize the vertical adjustment range or travel in prior hospital beds, without sacrificing stability, the mattress supporting structure is customarily mounted on a movable upper frame which interconnects, via motor-driven head and foot adjusting mechanisms, to a fixed lower base frame located close to the floor. The adjusting mechanisms are actuated to either lift or lower the upper frame, and consequently the mattress supporting structure, as desired. The lowermost level of the movable frame is most convenient when a patient is entering or leaving the bed. On the other hand, the uppermost height is generally preferred for examination and treatment of the patient. To enhance the patient's comfort, the mattress support is divided into a series of individually adjustable sections or panels that may be positioned, by independently operable motor-driven adjusting mechanisms, to provide a desired contour or configuration.
Switch actuators or push buttons included in a hand-held control device, or mounted on the bed and accessible to the patient, permit the patient to remotely control various functions or adjustments of the bed to select a desired height and a desired configuration for the mattress supporting structure. Additional switch actuators are sometimes mounted on a control panel, called a "nurse station", at the bed's foot end to enable the nurse, doctor or attendant to conveniently control some of the adjustments that are controllable by the patient, plus other adjustments that should not be controllable by the patient. For example, the trendelenburg and reverse trendelenburg controls are usually located at the nurse station. When the trendelenburg control is actuated, the entire mattress supporting structure is tilted or canted to a trendelenburg position (head end down, foot end up) and when the reverse trendelenburg control is depressed the mattress support is tilted to a reverse trendelenburg position (head end up, foot end down). The bed is adjusted to a trendelenburg position when the patient goes into shock, whereas a reverse trendelenburg position is employed for drainage.
Preferably, the nurse station should include switch actuators or push buttons for controlling the high-low or height adjustment of the movable frame. The high-low switches, controllable by the patient, are of the momentary contact type which requires the patient to maintain continuous pressure on spring-biased switch actuators until the desired bed height is reached. For the most efficient operation, the low switch at the nurse station should not necessitate continuous actuation by the nurse. Quite often, and especially at night, the bed is vertically adjusted by the nurse to its lower position obtainable. As an important time-saving feature for the nurse, the extreme low limit should be reached merely by momentarily depressing a spring-biased switch actuator or push button.
Hospital bed latching systems have been developed which are latched or locked in a down operating mode, in response to the actuation of a momentary contact switch, to run the movable frame to its low limit. This is known as the "walkaway down" feature since the nurse can walk away and leave the hospital room as soon as the bed starts descending. In all of these prior hospital beds, however, the movable frame must first be placed at a horizontal level before it can then be lowered all the way down to its low limit. If the bed is even slightly tilted at the time the nurse wishes to use the walkaway down feature, she must initially actuate some appropriate control (such as an "out of trendelenburg" control or an "out of reverse trendelenburg" control) in order to level the bed and then she can depress the low switch actuator to lower the bed to its desired lowermost level. Complicated, and sometimes confusing, steps must therefore be taken by the nurse, or some other operator, and substantial time is required to manipulate such prior hospital beds to their lowermost level positions.
These shortcomings have now been overcome. By only simple steps by the nurse, the hospital bed of the present invention may be shifted immediately and directly to its lowermost level, irrespective of its position at the time and even though it may be tilted. In other words, the bed may be moved, from any level and from any tilted position, directly to its lowermost limit. Among other advantages, this results in a significant time saving when the nurse adjusts the bed.